Infrared Photometry and Spectroscopy of VY Aqr and EI Psc: Two Short-Period Cataclysmic Variables With Curious Secondary Stars
We present new K-band spectra of VY Aqr and EI Psc obtained with NIRSPECon the Keck II telescope. We find a best-fitting spectral type of K4 forEI Psc, in agreement with the previous classification. The Keck spectrumof VY Aqr suggests an M0 spectral type, much hotter than previouslyderived. We re-reduce the original data for VY Aqr that were obtainedusing ISAAC on the Very Large Telescope (VLT) and find a best-fittingspectral type of M6 for VY Aqr. We are unable to reconcile the two datasets. We analyze new phase-resolved optical spectroscopy of VY Aqr,obtained using UVES on the VLT, to derive the mass ratio, and show thatthe mass of its secondary star is very likely below thestellar/substellar boundary. We also present and model phase-resolvedJHK infrared light curves for both objects, and g- and I-band lightcurves for EI Psc. While the light curve models for EI Psc areconsistent with its spectral type, we are unable to model the lightcurves of VY Aqr without assuming binary star parameters outside thepublished range for this object.Partly based on observations made with the ESO Telescopes at ParanalObservatory under programs 65.H-0409 (archival data) and 69.D-0391(A).
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The 2MASS Wide-Field T Dwarf Search. III. Seven New T Dwarfs and Other Cool Dwarf Discoveries
We present the discovery of seven new T dwarfs identified in the TwoMicron All Sky Survey. Low-resolution (R~150) 0.8-2.5 μm spectroscopyobtained with the Infrared Telescope Facility (IRTF) SpeX instrumentreveals the characteristic H2O and CH4 bands inthe spectra of these brown dwarfs. Comparison with spectral standardsobserved with the same instrument enables us to derive classificationsof T3 to T7 for the objects in this sample. Moderate-resolution (R~1200)near-infrared spectroscopy for a subset of these discoveries reveal K Iline strengths consistent with previously observed trends with spectraltype. Follow-up imaging observations provide proper-motion measurementsfor these sources, ranging from less than 0.1" to 1.55" yr-1.One object, 2MASS 0034+0523, has a spectrophotometric distance placingit within 10 pc of the Sun. This source also exhibits a depressed K-bandpeak reminiscent of the peculiar T dwarf 2MASS 0937+2931 and may be ametal-poor or old, high-mass brown dwarf. We also present low-resolutionSpeX data for a set of M- and L-type dwarf, subdwarf, and giantcomparison stars used to classify 59 additional candidates identified asbackground stars. These are primarily M5-M8.5 dwarfs, many exhibiting HI Paγ, but include three candidate ultracool M subdwarfs and onepossible early-type L subdwarf.
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Spectral Irradiance Calibration in the Infrared. XIV. The Absolute Calibration of 2MASS
Element by element, we have combined the optical components in the threecameras of the Two Micron All Sky Survey (2MASS), and incorporateddetector quantum efficiency curves and site-specific atmospherictransmissions, to create three relative spectral response curves (RSRs).We provide the absolute 2MASS attributes associated with ``zeromagnitude'' in the JHKs bands so that these RSRs may be usedfor synthetic photometry. The RSRs tie 2MASS to the``Cohen-Walker-Witteborn'' framework of absolute photometry and stellarspectra for the purpose of using 2MASS data to support the developmentof absolute calibrators for the Infrared Array Camera and pairwisecross-calibrators between all three SIRTF instruments. We examine therobustness of these RSRs to changes in water vapor within a night. Wecompare the observed 2MASS magnitudes of 33 stars (converted from theprecision optical calibrators of Landolt and Carter-Meadows intoabsolute infrared calibrators from 1.2 to 35 μm) with ourpredictions, thereby deriving 2MASS ``zero-point offsets'' from theensemble. These offsets are the final ingredients essential to merge2MASS JHKs data with our other absolutely calibrated bandsand stellar spectra, and to support the creation of faint calibrationstars for SIRTF.
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Spectral Irradiance Calibration in the Infrared. XIII. ``Supertemplates'' and On-Orbit Calibrators for the SIRTF Infrared Array Camera
We describe the technique that will be used to develop a set of on-orbitcalibrators for the Infrared Array Camera (IRAC) and demonstrate thevalidity of the method for stars with spectral types either K0-M0 III orA0-A5 V. For application to SIRTF, the approach is intended to operatewith all available optical, near-infrared (NIR), and mid-infrared (MIR)photometry and to yield complete absolute spectra from UV to MIR. Oneset of stars is picked from Landolt's extensive network of optical(UBVRI) calibrators, the other from the Carter-Meadows set of faint IRstandards. Traceability to the ``Cohen-Walker-Witteborn'' framework ofabsolute photometry and stellar spectra is assured. The method is basedon the use of either ``supertemplates,'' which represent the intrinsicshapes of the spectra of K0-M0 III stars from far-UV (1150 Å) toMIR (35 μm) wavelengths, or Kurucz synthetic spectra for A0-A5 Vstars. Each supertemplate or Kurucz model is reddened according to theindividual star's extinction and is normalized using availablecharacterized optical photometry. This paper tests our capability topredict NIR (JHK) magnitudes using supertemplates or models constrainedby Hipparcos/Tycho or precision ground-based optical data. We provideabsolutely calibrated 0.275-35.00 μm spectra of 33 Landolt andCarter-Meadows optical standard stars to demonstrate the viability ofthis technique, and to offer a set of IR calibrators 100-1000 timesfainter than those we have previously published. As an indication ofwhat we can expect for actual IRAC calibration stars, we have calculatedthe absolute uncertainties associated with predicting the IRACmagnitudes for the faintest cool giant and hot dwarf in this new set ofcalibration stars.
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Infrared spectroscopy of the supersoft X-ray source MR Vel
We describe the infrared spectrum of the galactic supersoft X-ray sourceMR Vel (RX J0925.7-4758) in the wavelength range of 1.1-2.6 mu m. Wefind Paschen, Brackett, He I, He II and neutral and ionized oxygen linesin emission. No traces of the secondary star were found. P-Cygniprofiles were observed in Paschen beta and Brackett gamma , from whichwe conclude that these lines arise in a wind. Fitting the optical andinfrared energy distribution with a supercritical disk model,incorporating white dwarf and secondary star contributions, we were ableto constrain the distance to 2-5 kpc, which implies an absolutemagnitude MV between -2 and 0.
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A search for brown dwarf like secondaries in cataclysmic variables
We present VTL/ISAAC infrared spectroscopy of a sample ofshort-orbital-period cataclysmic variables that are candidates forharbouring substellar companions. We have detected the K I and Na Iabsorption lines of the companion star in VY Aqr. The overall spectraldistribution in this system is best fitted with an M9.5 type dwarfspectrum, implying a distance of 100 +/- 10 pc. VY Aqr seems to fall farfrom the theoretical distribution of secondary star temperatures aroundthe orbital period minimum. Fitting of the IR spectral energydistribution (SED) was performed by comparing the observed spectrum withlate-type templates. The application of such a spectral fittingprocedure suggests that the continuum shape in the 1.1-2.5 ?mspectral region in short-orbital-period cataclysmic variables may be auseful indicator of the companion's spectral type. SED fitting for RZLeo and CU Vel suggests M5-type dwarf companions, and distances of 340+/- 110 and 150 +/- 50 pc, respectively. These systems may be placed inthe upper evolution branch for short-period cataclysmic variables.
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New aperture photometry for 217 galaxies in the Virgo and Fornax clusters.
We present photo electric multi-aperture photometry in UBVRI of 171 and46 galaxies in the Virgo and Fornax clusters, respectively. Many of thegalaxies have not been observed in at least one of these passbandsbefore. We discuss the reduction and transformation into the Cousinsphotometric system as well as the extinction coefficients obtainedbetween 1990 and 1993.
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Fainter Southern JHK Standards Suitable for Infrared Arrays
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995MNRAS.276..734C&db_key=AST
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A homogeneous catalog of new UBV and H-beta photometry of B- and A-type stars in and around the Scorpius-Centaurus OB association
B- and A-type stars in and near the Sco-Cen OB association areinvestigated with UBV and H-beta photometry to acquire data relevant tothe luminosity function of Sco-Cen. The measurements generally consistof two 10-s integrations of U, B, V, (W, N) filters, and theobservations are corrected iteratively for atmospheric extinction andinstrumental response. The data presented give the mean V magnitude,mean B-V, mean U-B, and the estimated uncertainties for these values.The catalog provides a homogeneous catalog of data for a large fieldwith stellar objects delineating membership to the association Sco-Cenand that affect the luminosity function of the aggregate.
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Secondary UVBY standards in the Harvard E-regions
Photoelectric uvby photometry for 201 stars which are already UBV (RI)cstandards is presented. The photoelectric data are closely tied to theCousins uvby standards and the stars should be suitable for use asfainter (7-11 mag) secondary standards.
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Secondary standards for H-beta photometry in the Southern Hemisphere (second series).
Not Available
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UBV (RI)c standard stars in the E- and F-regions and in the Magellanic Clouds - a revised catalogue.
Not Available
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The Baade-Wesselink method applied to field RR Lyrae stars. I - UBVRI photoelectric and radial velocity data
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1987A&AS...69..135C&db_key=AST
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Secondary standards for the Stromgren UVBY system
Observations of 158 E region stars have been made in the Stromgrensystem, using the 46-cm reflector at Cape Town. They are mostly brighterthan eighth magnitude and are intended for use as secondary standardsfor the four-color system. The E region relative zero points are definedwith a precision of + or - 0.001 mag, and the internal standard errorsof the colors life between + or - 0.001 and + or - 0.002 mag.
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UBV photometry of E region standard stars of intermediate brightness
Photometry data are given for 335 stars in the nine E regions.Observations were made using a photometer and filters on the 47 cmreflector at Cape Town. The stellar dispersions are summarized. Data arepresented in tabular form.
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Note on the Photometric Properties of Red Dwarfs in the Cousins VRI System
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1981A&AS...46..105T&db_key=AST
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Photometric standard stars for the UBV and (RI)KC systems.
Not Available
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Fainter Standards for VRI Photometry in the E Regions
Not Available
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UBV photometry for star clusters in the Small Magellanic Cloud.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1978A&AS...34..431A&db_key=AST
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A photoelectric UBV sequence in the region of the wing of the Small Magellanic Cloud
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1978A&AS...33..107J&db_key=AST
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VRI standards in the E regions
Not Available
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Standard Stars for VRI Photometry with S25 Response Photocathodes [Errata: 1974MNSSA..33....1C]
Not Available
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Lichtelektrische UBV-Photometrie von Standardsternen und in vier Sternfeldern am Äquator
Not Available
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Standard magnitudes in the E regions.
Not Available
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